1. Field of the Invention
The present invention relates to management of production lines producing various products and, more particularly, to a production management method in production of products with loads distributed over a plurality of production lines.
2. Description of the Background Art
Various methods for making production plans have been conventionally developed, as a production management system, for the purposes of controlling a relation between a production capacity and a load with certainty, to level a load, and to observe delivery times. Especially, as for making a production plan for a production process having many steps, as in an assembling, in which a multiple kinds of basic parts are sequentially assembled into intermediate parts to eventually fabricate a finished product, the following are exemplified.
Japanese Patent Laying-Open No. 2000-158300 discloses a method for making a production plan capable of easily making an excellent plan giving simultaneous consideration to a relation between a capacity and a load, possibility in procurement of materials, leveling of a load, observance of delivery times and others. This method for making a production plan includes the steps of: performing development using a MRP system under production number control with delivery time information, production information, inventory information and calendar information to prepare a string-attached MRP development information; evaluating constraints of the prepared string-attached MRP development information based on material delivery schedule information and capacity information to extract information associated with a constraint-violated order from the string-attached MRP development information based on a result of the evaluation; and correcting the string-attached MRP development information associated with the extracted violated order based on the material delivery schedule information and the capacity information to thereby adjust a production plan.
According to this method for making a production plan, since mutual reference is enabled between a series of string-attached demands and orders, an influence of the adjustment on the other product items can be instantly judge with result that adjustment is enabled of a plan in which consideration is given to an influence to all of the product items and all of the process; thereby enabling a plan adjusting time to be reduced and furthermore, improvement on a quality of the plan. Furthermore, an increase in load beyond the capacity is enabled, and adjustment is enabled for a plan in which the load exceeds the capacity without performing a re-trial through a modification on capacity information and for a plan in which the load is lower than the capacity but leveled, thereby, enabling a plan adjusting time to be reduced and improvement on a quality of the plan.
Furthermore, Japanese Patent Laying-Open No. 9-128440 discloses a production planning system in which a production plan is analyzed to thereby narrow down adjustment contents for extracting a problematic point or improving a plan and to further enable decision making support. for a person in charge of production planning in plan adjustment. This production planning system handles production processes for items constituting a finished product each as at least one shop relative to a completion schedule showing a completion date and a numerical volume and others of the finished product requested by a user to calculate a period capable of producing the item in each shop and to thereby determine a production schedule till the finished product is completed, includes: means for controlling operating capacities of the shops and spare capacities of the shops derived from the operating capacities and operating loads imposed on the shops; means for determining dates on which operating loads necessary for the finished product are secured from the spare capacities of the shops in case where no production schedule is enabled that meets a completion date defined by the completion schedule; and means for calculating a production enabling date for the finished product based on the dates determined on the respective shops.
According to the production planning system, since a planner has conventionally determined satisfactory adjustment contents from adjustment contents having a high degree of freedom using a great volume of data as an object, much of time is spent in studying because of various kinds of try and error in adjustment, whereas according to a production planning system of the present invention, items, which are objects for planning, or planning statuses of shops are analyzed concerning a plan including a problem; thereby enabling a proposal, in a short time, on a adjusted draft for making a plan capable of implementing and in turn enabling reduction in time spent for making a production plan meeting an evaluation measure of the planner. That is, a spare capacity of each shop is analyzed, thereby enabling a proposal on a adjusted draft in a case where a change in a completion schedule occurs or the like case.
In making a production plan in a semiconductor fabrication process or the like, when a demand (an order volume from a customer, who is a purchaser of a product) is larger than a production capacity, a production is executed by organizing a parallel production model in which a plurality of production lines are included in consideration of load allocation over the production lines. In a drafting of a production plan, a just-in-time scheme (in which necessary volumes of necessary items are produced when being necessary) is usually adopted because of compression of inventory assets. For this reason, a production plan is made so as to realize the shortest lead time and to minimize stock in process and stock as a finish product. As a result, load distribution over capacities of a plurality of production lines is inevitably in a parallel fashion.
Once scheduling is performed with a model for a parallel production plan, load distribution is forced to be in a parallel fashion. In a case where a production line is temporarily ceased for some reason or other, however, load is unbalanced to be distributed on other limited operable production lines. In addition thereto, there also exists a factor that when a new production line is put into operation, a product from the new line can be delivered to the customer for the first time after an approval of the customer for the new production line. A problem arises that production conditions are complicated in a case where a plurality of lines are operated to implement parallel production in this way.
Facing such a problem, however, no solution therefor can be given with applications of the method for making a production plan disclosed in Japanese Patent Laying-Open No. 2000-158300 described above and the production planning system disclosed in Japanese Patent Laying-Open No. 9-128440; therefore, manual processing has been adopted to cope with the problem. That is, a cease of production and supply such as a temporary cease of a production line can be controlled using a holiday calendar set in each production line, whereas a perfect production management is disabled that includes a condition of whether or not adaptability for a specific customer in delivery, quality or the like can be achieved in each production line.
It is an object of the present invention to provide a production management method in a plurality of production lines.
It is another object of the present invention to provide a production management method in a plurality of production lines in consideration of various constraint conditions associated with the production lines.
It is still another object of the present invention to provide a production management method in a plurality of production lines in consideration of restraint conditions, designated by a purchaser, and associated with the production lines.
It is yet another object of the present invention to provide a production management method in a plurality of production lines in consideration of constraint conditions for maintenance associated with the production lines.
A production management method according to the present invention is a production management method for performing parallel production in a plurality of production lines including the steps of: storing order information concerning an order volume and a delivery time thereof from a purchaser; storing cease period information concerning a cease period of a production line; storing authentication information concerning authentication of a production line from the purchaser; detecting a volume in process in the plurality of production lines; calculating an additional input volume on the basis of the volume in process and the order volume; calculating a scheduled production completion date in consideration of the cease period for an input lot for which the authentication information is obtained; and allocating the input lot to the order information on the basis of the scheduled production completion date and the delivery time.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.